System and a method for determining a radiation pattern

Abstract

A system for determining the radiation pattern of an antenna array comprising a plurality of antenna elements comprises a signal generator for generating a test signal, a number of probes for measuring a magnitude of the signals emitted by the antenna elements when driven with the test signal in a first surface and in a second surface, wherein the distance of the first surface to the antenna elements is smaller than the distance of the second surface to the antenna elements, and a pattern calculation unit for calculating the radiation pattern of the antenna array based on the magnitudes measured in the first surface and the second surface.

The invention claimed is: 
     
       1. A system for determining the radiation pattern of an antenna array comprising a plurality of antenna elements, the system comprising:
 a signal generator for generating a test signal, 
 a number of probes for measuring a magnitude of the signals emitted by the antenna elements when driven with the test signal in a first surface and in a second surface, wherein a first distance of the first surface to the antenna elements is smaller than a second distance of the second surface to the antenna elements, and wherein the aperture of the probes used at the first distance is smaller than the aperture of the probes used at the second distance, and 
 a pattern calculation unit for calculating the radiation pattern of the antenna array based on the magnitudes measured in the first surface and the second surface. 
 
     
     
       2. The system of  claim 1 , wherein the test signal when applied to the antenna elements drives the antenna elements to emit a static radio frequency (RF) signal. 
     
     
       3. The system of  claim 1 , wherein the test signal is provided as a digital command signal to a signal processing unit of the antenna array. 
     
     
       4. The system of  claim 1 , wherein the test signal is provided as a RF signal for driving each of the antenna elements directly. 
     
     
       5. The system of  claim 1 , wherein the distance of the first surface to the antenna elements is such that the measured magnitudes allow differentiating the antenna elements and the distance of the second surface is such that the measured magnitudes do not allow differentiating the antenna elements. 
     
     
       6. The system of  claim 1 , wherein the first distance is between Δd and two times Δd, wherein Δd is the distance between the antenna elements in the antenna array. 
     
     
       7. The system of  claim 1 , wherein the antenna array comprises a radom and the first distance is the distance of the radom's outer surface to the antenna array. 
     
     
       8. The system of  claim 1 , wherein the aperture of the probes used at the first distance or the second distance is defined as the distance of the two end points of an arc segment in the first distance or the second distance, respectively, the arc segment comprising an angle 
       
         
           
             
               α 
               = 
               
                 
                   tan 
                   
                     - 
                     1 
                   
                 
                 ⁡ 
                 
                   ( 
                   
                     
                       λ 
                       0 
                     
                     
                       L 
                       max 
                     
                   
                   ) 
                 
               
             
           
         
       
       wherein λ 0  is the wavelength of the test signal, and L max  is the radius of the smallest sphere, which surrounds the antenna array. 
     
     
       9. The system of  claim 1 , wherein the aperture of the probes used at the first distance is defined as 
       
         
           
             
               
                 W 
                 
                   D 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   1 
                 
               
               ≤ 
               
                 
                   λ 
                   0 
                 
                 2 
               
             
           
         
       
       wherein λ 0  is the wavelength of the test signal. 
     
     
       10. The system of  claim 1 , wherein the aperture of the probes used at the second distance is defined as 
       
         
           
             
               
                 
                   W 
                   
                     D 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     2 
                   
                 
                 ≤ 
                 
                   
                     D 
                     2 
                   
                   * 
                   tan 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   α 
                 
               
               , 
               with 
             
           
         
         
           
             
               α 
               = 
               
                 
                   tan 
                   
                     - 
                     1 
                   
                 
                 ⁡ 
                 
                   ( 
                   
                     
                       λ 
                       0 
                     
                     
                       L 
                       max 
                     
                   
                   ) 
                 
               
             
           
         
       
       wherein D 2  is the second distance, λ 0  is the wavelength of the test signal, and L max  is the radius of the smallest sphere, which surrounds the antenna array. 
     
     
       11. The system of  claim 1 , wherein the first surface and/or the second surface comprise at least a section of a sphere and/or an ellipsoid and/or a cylinder, especially wherein the first surface and/or the second surface comprise different shapes. 
     
     
       12. The system of  claim 1 , comprising a mechanical structure, which is rotatable around a first axis and comprises at least one probe at the first distance from the first axis and at least on other probe at the second distance from the first axis. 
     
     
       13. A method for determining the radiation pattern of an antenna array comprising a plurality of antenna elements, the method comprising:
 generating a test signal and driving the antenna elements with the generated test signal, 
 measuring a magnitude of the signals emitted by the antenna elements when driven with the test signal with a number of probes in a first surface and in a second surface, wherein a first distance of the first surface to the antenna elements is smaller than a second distance of the second surface to the antenna elements, and wherein the aperture of the probes used at the first distance is smaller than the aperture of the probes used at the second distance, and 
 calculating the radiation pattern of the antenna array based on the magnitudes measured in the first surface and the second surface. 
 
     
     
       14. The method of  claim 13 , wherein the test signal when applied to the antenna elements drives the antenna elements to emit a static radio frequency (RF) signal. 
     
     
       15. The method of  claim 13 , wherein the test signal comprises a digital command signal to a signal processing unit of the antenna array. 
     
     
       16. The method of  claim 13 , wherein the test signal is provided as a RF signal for driving each of the antenna elements directly. 
     
     
       17. The method of  claim 13 , wherein the distance of the first surface to the antenna elements is such that the measured magnitudes allow differentiating the antenna elements and the distance of the second surface is such that the measured magnitudes do not allow differentiating the antenna elements. 
     
     
       18. The method of  claim 13 , wherein the first distance is between Δd and two times Δd, wherein Δd is the distance between the antenna elements in the antenna array. 
     
     
       19. The method of  claim 13 , wherein the antenna array comprises a radom and the first distance is the distance of the radom's outer surface to the antenna array. 
     
     
       20. The method of  claim 13 , wherein the aperture of the probes used at the first distance or the second distance, respectively, is defined as the distance of the two end points of an arc segment in the first distance or the second distance, respectively, the arc segment comprising an angle 
       
         
           
             
               α 
               = 
               
                 
                   tan 
                   
                     - 
                     1 
                   
                 
                 ⁡ 
                 
                   ( 
                   
                     
                       λ 
                       0 
                     
                     
                       L 
                       max 
                     
                   
                   ) 
                 
               
             
           
         
       
       wherein λ 0  is the wavelength of the test signal, and L max  is the radius of the smallest sphere, which surrounds the antenna array. 
     
     
       21. The method of  claim 13 , wherein the aperture of the probes used at the first distance is defined as 
       
         
           
             
               
                 W 
                 
                   D 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   1 
                 
               
               ≤ 
               
                 
                   λ 
                   0 
                 
                 2 
               
             
           
         
       
       wherein λ 0  is the wavelength of the test signal. 
     
     
       22. The method of  claim 13 , wherein the aperture of the probes used at the second distance is defined as 
       
         
           
             
               
                 
                   W 
                   
                     D 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     2 
                   
                 
                 ≤ 
                 
                   
                     D 
                     2 
                   
                   * 
                   tan 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   α 
                 
               
               , 
               with 
             
           
         
         
           
             
               α 
               = 
               
                 
                   tan 
                   
                     - 
                     1 
                   
                 
                 ⁡ 
                 
                   ( 
                   
                     
                       λ 
                       0 
                     
                     
                       L 
                       max 
                     
                   
                   ) 
                 
               
             
           
         
       
       wherein D 2  is the second distance, λ 0  is the wavelength of the test signal, and L max  is the radius of the smallest sphere, which surrounds the antenna array. 
     
     
       23. The method of  claim 13 , wherein the first surface and/or the second surface comprise at least a section of a sphere and/or an ellipsoid and/or a cylinder, especially wherein the first surface and/or the second surface comprise different shapes.